The difference between his broken stones and the more or less rounded stones with which the roads were then being repaired was, McAdam declared, the difference between the stones that were thrown down in a stream to form a ford and the shaped stones used to construct the bridge that went over the stream; while inasmuch as the road-arch, or crust, he {104}formed would rest on the ground, and be impermeable to rain-water, there would be no need to have underneath it either a stone foundation or a system of drainage; though he held it as essential that the subsoil should be perfectly dry when the "metal," or covering of broken stone, was laid in position. Keeping the water out of the road by this means, he would prevent the road itself from being broken up by the action of frost, and he would have a more elastic surface than if there were a solid stone foundation under the metal. The thickness of his consolidated cover of broken stones would, he further argued, be immaterial to its weight-carrying capacity. In 1816 McAdam became surveyor of roads in the Bristol district, and the object lessons in road-mending which he provided there were so convincing that his system began to be generally approved in 1818. In 1827 he was appointed Surveyor-General of Roads, and in the same year he issued a ninth edition of his "Remarks on the Present System of Road-Making." In this publication he states, among other things, that very considerable sums were being raised annually in the kingdom, principally from tolls, on account of turnpike roads, and these funds were expended, nominally under the protection of Commissioners, but practically under the surveyors. Every Session there were numerous applications to Parliament by turnpike trusts for powers to increase their tolls in order to pay off their debts and to keep the roads in repair. In the Session of 1815 there were 34 such petitions; in 1816 there were 32, and "all passed as a matter of course." The condition of the turnpike roads was, nevertheless, most defective, and that of the parish roads was "more deplorable than that of the turnpike roads." Legislative enactments for the maintenance and repair of the parish roads were so inadequate that these roads "might be considered as being placed almost out of the protection of the law." In the result "The defective state of the roads, independent of the unnecessary expense, is oppressive on agriculture, commerce and manufactures by the increase of the price of transport, by waste of the labour of cattle, and wear of carriages, as well as by causing much delay of time."